The present invention relates to an improvement in pulmonary dosing systems of the type taught in U.S. Pat. No. 6,269,810, wherein a diffuser baffle is provided in the plenum of the pulmonary dosing system to improve dosing efficiency.
The invention relates to a pulmonary dosing system and method for supplying to a patient a predetermined amount of respirable therapeutically active material in an aerosolized form, and more particularly to such a system and method which is compact, self-contained, and capable of supplying any respirable therapeutically active material, including toxic drugs such as chemotherapy drugs, wherein a diffuser baffle is utilized in the plenum of the system to improve dosing efficiency.
The pulmonary dosing system described in commonly assigned U.S. Pat. No. 6,269,810 to Brooker et al. is able to contain the therapeutically active material or drug to the extent that it can safely administer toxic drugs such as chemotherapy drugs. The respirable therapeutically active material is aerosolized, typically by being entrained in pulses of air synchronized with the patient""s exhalations. Except for the inhalation tube, the exhalation tube and the patient interface connected thereto, the remainder of the inhalation and exhalation portions of the system including the delivery apparatus for the therapeutically active material may be located in a sealed containment case. The containment case may be subjected to a mild vacuum from a vacuum source including a filter to further assure containment of the therapeutically active material, if necessary. Alternatively, the system may be provided with an active flow system for ensuring flow through the system. The system may be provided with a control unit containing a compressor and valve to provide pulsed air, a vacuum pump to provide the mild vacuum within the containment case, and a computer with inputs from various sensor devices together with a number of interfaces with the operator and with the patient.
One of the more advantageous features of the Brooker et al. drug delivery or pulmonary dosing system is its efficiency in delivering drugs. This may be particularly important with respect to the time spent by the patient and the support staff for each treatment and also with respect to reducing the expense of extremely costly drugs. The efficiency refers not only to the efficiency of delivering drug to the patient (not lost in the delivery system), but also to the efficiency of getting the delivered drug to penetrate deep into the lung of the patient to provide the needed therapy. The present invention may reduce the amount of aerosolized drug that may be deposited in the mouth, the upper airway, or the nasal cavity.
One of the novel features which adds to this efficiency is the combination of the nebulizer (or other aerosol-producing device), the plenum with a diffuser baffle, an air supply and the control system, which are combined to provide a metered dose of drug and air to the patient at the designated time for inhalation. In one efficient operation, the aerosol-producing device is controlled to deliver a selected volume of drug aerosol to the plenum prior to the inhalation phase of the patient. As described herein, this can be performed by sensing the exhalation phase of the patient and then providing a pulse of air to the nebulizer which results in a metered volume of aerosolized drug in the plenum. Sensing the exhalation phase of the patient may include automatic sensing or manual sensing, as by the patient or operator.
The diffuser baffle prevents axial flow of the aerosolized dose from the inlet to the outlet of the plenum, thereby more efficiently utilizing the available volume in the plenum such that the aerosolized dose is retained in the plenum and the inhalation tube until the inhalation phase is initiated. The disruption of axial flow of the aerosolized dose provided by the diffuser baffle reduces or eliminates the loss of drug into the exhale tube. The loss of drug associated with the flow of the aerosolized dose into the exhale tube prior to the start of the inhalation phase is referred to as xe2x80x9cblow-by.xe2x80x9d This phenomenon causes inefficient operation of the pulmonary dosing system as well as loss of expensive drug. The inability to control xe2x80x9cblow-byxe2x80x9d interferes with the delivery of an accurate and predictable delivered dose. The diffuser baffle in the plenum improves the reproducibility with which an accurate dose can be delivered by increasing the retention of the aerosolized dose in the chamber and minimizing or eliminating xe2x80x9cblow-byxe2x80x9d of the drug.
The present invention is directed to an improved system for pulmonary dosing and, in particular, to an improved plenum useful in a pulmonary dosing system similar to that disclosed in U.S. Pat. No. 6,269,810 to Brooker et al., the contents of which are incorporated herein by reference. The plenum chamber of the present invention comprises an inlet for receiving aerosolized doses from an aerosolizer source and an outlet for connection to a patient interface, wherein the inlet and outlet are oriented along a common axis in the plenum chamber, and a diffuser baffle is positioned on that axis and interposed between the inlet and outlet. The diffuser baffle interrupts the direct flow of the aerosolized dose along the axial path between the plenum chamber inlet and outlet thereby preventing direct flow of the aerosolized dose through the chamber and possible loss of drug into the exhale tube. The aerosolized dose is diverted by the diffuser baffle thereby efficiently utilizing the available volume of the plenum chamber. The dose is held in the chamber and the inhale tube until the patient inhales.
Many pharmaceutical agents such as chemotherapy drugs are both toxic and expensive. This means that it is very important to use these drugs efficiently and safely. It has been found that the plenum shown in the Brooker patent produces an axialized flow of the medicament. The annular volumes within the chamber tend to be somewhat stagnant and aerosolized pulses can move directly through the chamber. When this occurs the dose is not used efficiently. It has been found advantageous to disrupt this flow, however, it has also been found that vortical flow that maximizes exposure of the medicament to the surface of the plenum is not desirable as the medicament may adhere to the surface of the plenum and not be inhaled by the patient.
In accordance with certain embodiments of the invention, there is provided a pulmonary dosing system and method for supplying to a patient a predetermined amount of respirable therapeutically active material. The system may comprise a patient interface to introduce the material into the patient""s lungs. This interface may constitute a mouth piece, a mask and mouth tube combination, an endotracheal tube, a nasal tube, or the like. The patient interface is connected to a flexible inhalation tube and a flexible exhalation tube. The exhalation tube is connected to a filter, the outlet of which is connected to atmosphere. The inhalation tube is connected to an apparatus for providing pulsed amounts of the material entrained in filtered atmospheric air. The apparatus may comprise a nebulizer having an inlet for pulsed air, a plenum chamber with a diffuser baffle and a connection, provided with a filter, to atmospheric air.
A control system may be provided to operate the pulmonary dosing system in accordance with operator inputs selecting the number of patient breaths between pulses, the pulse length, and the number of pulses required to provide the prescribed amount of material to be dispensed to the patient. The exhaust filter and the apparatus for providing pulsed amounts of the therapeutically active material may be enclosed in a containment case. The dosing system is capable of supplying at least one non-toxic drug, or at least one toxic drug to the patient.